Almost every individual has a measurable deterioration of cognitive abilities as he or she ages. The experience of this decline may begin with occasional lapses in memory in one's thirties, such as increasing difficulty in remembering names and faces, and often progresses to more frequent lapses as one ages in which there is passing difficulty recalling the names of objects, or remembering a sequence of instructions to follow directions from one place to another. Typically, such decline accelerates in one's fifties and over subsequent decades, such that these lapses become noticeably more frequent. This is commonly dismissed as simply “a senior moment” or “getting older.” In reality, this decline is to be expected and is predictable. It is often clinically referred to as “age-related cognitive decline,” or “age-associated memory impairment.” While often viewed (especially against more serious illnesses) as benign, such predictable age-related cognitive decline can severely alter quality of life by making daily tasks (e.g., driving a car, remembering the names of old friends) difficult.
In many older adults, age-related cognitive decline leads to a more severe condition now known as Mild Cognitive Impairment (MCI), in which sufferers show specific sharp declines in cognitive function relative to their historical lifetime abilities while not meeting the formal clinical criteria for dementia. MCI is now recognized to be a likely prodromal condition to Alzheimer's Disease (AD) which represents the final collapse of cognitive abilities in an older adult. The development of novel therapies to prevent the onset of this devastating neurological disorder is a key goal for modern medical science.
The majority of the experimental efforts directed toward developing new strategies for ameliorating the cognitive and memory impacts of aging have focused on blocking and possibly reversing the pathological processes associated with the physical deterioration of the brain. However, the positive benefits provided by available therapeutic approaches (most notably, the cholinesterase inhibitors) have been modest to date in AD, and are not approved for earlier stages of memory and cognitive loss such as age-related cognitive decline and MCI.
Cognitive training is another potentially potent therapeutic approach to the problems of age-related cognitive decline, MCI, and AD. This approach typically employs computer- or clinician-guided training to teach subjects cognitive strategies to mitigate their memory loss. Although moderate gains in memory and cognitive abilities have been recorded with cognitive training, the general applicability of this approach has been significantly limited by two factors: 1) Lack of Generalization; and 2) Lack of enduring effect.
Lack of Generalization: Training benefits typically do not generalize beyond the trained skills to other types of cognitive tasks or to other “real-world” behavioral abilities. As a result, effecting significant changes in overall cognitive status would require exhaustive training of all relevant abilities, which is typically infeasible given time constraints on training.
Lack of Enduring Effect: Training benefits generally do not endure for significant periods of time following the end of training. As a result, cognitive training has appeared infeasible given the time available for training sessions, particularly from people who suffer only early cognitive impairments and may still be quite busy with daily activities.
As a result of overall moderate efficacy, lack of generalization, and lack of enduring effect, no cognitive training strategies are broadly applied to the problems of age-related cognitive decline, and to date they have had negligible commercial impacts. The applicants believe that a significantly innovative type of training can be developed that will surmount these challenges and lead to fundamental improvements in the treatment of age-related cognitive decline. This innovation is based on a deep understanding of the science of “brain plasticity” that has emerged from basic research in neuroscience over the past twenty years which only now through the application of computer technology can be brought out of the laboratory and into the everyday therapeutic treatment.
Some cognition improvement exercises, such as embodiments of the Tell Us Apart exercise in the HiFi program described herein, are designed to force participants to identify rapid spectro-temporal patterns (brief synthesized formant transitions) in order to classify consonants by place of articulation under conditions of backward masking from a following vowel. The spectral characteristics of these syllables (as dictated by formant frequencies) closely parallel the patterns that occur in natural productions of the sounds, and they can usually be identified as the speech sounds they are intended to represent. However, since formant frequencies constitute only a (comparatively informative) subset of the range of acoustic cues that accompany human productions of the consonants, sounds synthesized in this way do not closely resemble natural speech in a general sense.
As a result, many participants may be unable to match these synthesized sounds, presented in isolation, with the intended syllables based on their previous linguistic experience, and are therefore unable to progress through the easiest levels of the exercise, which almost certainly involve sound distinctions that are well above their actual thresholds for detection.
More generally, in exercises that use synthesized speech to target specific neurological deficits, it is desired that the effectiveness of a task not be severely limited by the overall naturalness of the speech stimuli, since it is often necessary to reduce the acoustic cues available to the listener to a small, carefully controlled set. Thus, a way is needed to help listeners attend to the set of cues relevant to a synthetic speech distinction so that they can reliably identify sounds and progress through the exercise.
Therefore, what is needed is an overall training program that will significantly improve fundamental aspects of brain performance and function relevant to the remediation of the neurological origins and consequences of age-related cognitive decline. Additionally, improved means for helping listeners attend to the set of cues relevant to a synthetic speech distinction to reliably identify sounds and progress through exercises that utilize such distinctions.